Flattening mill

ABSTRACT

A rolling mill for rectifying or avoiding undesirable shape in rolled products comprises flexible upper and lower work rolls, each work roll being backed either directly or through an intermediate roll by a single row of axially short backing rolls, each of which is carried in a carrier pivoted to a rigid member of the mill frame, the pivots of all the carriers associated with each work roll being aligned with one another, said mill including means for applying a substantially constant loading force to each of said carriers, the work rolls also being contacted by reaction rolls which contact the work rolls in such a manner that the reaction is substantially parallel with the plane of the strip pass between the work rolls to absorb the loads which arise in at least one direction parallel to the strip during rolling.

United States Patent [191 [111 3,724,252

Baker et al. 1 Apr. 3, 1973 [541 FLATTENING MILL 3,478,559 11/1969 Polakowski ..72 245 Inventors: Albert Baker, Walton-on- OR Thames, Surrey; Anthony Sydney Charles Barker, Deddington, Ox- 1,134,635 11/1968 Great Britain ..72/241 fordshire; John James Edmund Holden, Chester, Che hi St l Primary Examiner-Richard J. Herbst Pilkin mn Wint rb B b AttorneyR0bert S. Dunham, P. E. Henninger, Lester Oxfordshire, all of England W. Clark, Thomas F. Moran, Christopher C. Dunham d R b t S b [73] Assignee: Alcan Research and Development an 0 H CO ey Limited, Montreal, Quebec, Canada [57] ABSTRACT I [22] Flled: Sept 1970 A rolling mill for rectifying or avoiding undesirable [21] Appl. No: 76,566 shape in rolled products comprises flexible upper and lower work rolls, each work roll being backed either directly or through an intermediate roll by a single {30] Forelgn Apphcauon Pnomy Data row of axially short backing rolls, each of which is car- Oct. 3, 1969 Great Britain ..48,833/69 ried in a carrier pivoted to a rigid member of the mill frame, the pivots of all the carriers associated with [52] US. Cl ..72/241 each work roll being aligned with one another, said [51] Int. Cl. ..B2lb 13/14 mill including means for applying a substantially con- [58] Field of Search ..72/24l, 242, 243 stant loading force to each of said carriers, the work rolls also being contacted by reaction rolls which con- [56] References Cited tact the work rolls in such a manner that the reaction is substantially parallel with the plane of the strip pass UNITED STATES PATENTS between the work rolls to absorb the loads which arise 2,792,730 5/1957 Cozzo ..72/24l in at least one direction parallel to the strip during 2,878,778 3/1959 Kusters rolling. 2,651,954 9/1953 Dahlstrom.. 2,677,978 5/ 1954 Dahlstrom ..72/245 10 Claims, 10 Drawing Figures PATENTEDAPR 3 1975 SHEET l 0F 5 PATENTEDAPR 3 ms SHEET 5 BF 5 FLATTENING MILL The present invention relates to rolling apparatus and is particularly directed to a rolling mill for rectifying bad shape in rolled products, although a rolling mill may be constructed in accordance with the principles of the present invention for producing rolled products in which bad shape is avoided or held to a minimum.

In U.S. Pat. No. 3,429,166 there is described a rolling mill in which'the work rolls are thin and flexible and are backed by two or more rows of axially short backing rolls through which the vertical rolling load is imposed on the work rolls. Each of the work rolls is backed by such backing rolls and a substantially equal loading force .is applied to each of the backing rolls in each row of backing rolls. The backing rolls also resist the horizontal loads on the work rolls. As described in that specification the force is applied to the backing rolls by means of a hydraulic capsule which extends for the full length of the adjacent work roll. Each of the axially short backing rolls is carried in a common carrier with an adjacent backing roll in another row of backing rolls and each of the carriers is subjected to the pressure of the hydraulic capsule. In order to match the loaded width of the work rolls with the width of the strip being rolled, spring-loaded hooks are provided for the purpose of resisting the whole or part of the force applied to the work roll carriers by the hydraulic capsule.

As described in U.S. Pat. No. 3,429,166 the carriers for the backing rolls were either guided for vertical movement in the mill frame or were pivoted to the mill frame so that the carriers were held against longitudinal movement by the pivots. The latter arrangement was preferred because it eliminated the possibility of misalignment between the upper and lower work roll which could arise through the slight lateral movement (in the longitudinal direction of the strip path) of the individual carriers in the guideways associated with the mill beam.

It has however been found that very slight misalignment of the pivot axes of the individual roll carriers can lead to unacceptably large errors in the vertical forces applied to the work roll through the backing roll. It has been shown that non-uniformity of the load to the extent of a few per cent can cause unacceptable bad shape in the product of the flexible work roll mill and that misplacement of the pivots of the backing roll carriers by amounts of only a few ten-thousandths of an inch can cause unacceptable rolling load errors. It would be difiicult and costly to avoid misplacement errors of this magnitude. 1

It is therefore a principal object of the present invention to provide an improved form of rolling mill operating on the same general principles but avoiding the necessity for the extreme accuracy in positioning the pivots of the backing roll carriers.

Another difiiculty experienced with the apparatus described in U.S. Pat. No. 3,429,166 is the possibility .of flow of hydraulic fluid to one end of one hydraulic provided with spring-loaded latches for matching the loaded width of the work roll to the width of the strip passing between the work rolls. It is found that the outermost loaded backing rolls must apply loads to the work rolls adjusted to within about one-eighth inch of the strip width. Unless the loading applied by the backing rolls is matched with the product width within the above accuracy the strip will have bad shape through being either long edged or long middled.

According to a further feature of the invention there is an improved system for matching the loaded width of the work rolls with the width of the product and in particular for adjusting the load applied through the outermost loaded elements to the backing roll which responds automatically to the strip width.

Although in U.S. Pat. No. 3,429,166 we have described an apparatus in which the backing rolls in one row are staggered in relation to the backing rolls in the adjacent row great difficulty is experienced in manufacturing such apparatus and in practice it has not been found possible by use of this expedient to avoid the formation of marks on the work rolls by the backing rolls.

According to the invention a rolling mill comprises flexible upper and lower work rolls, each work roll being backed either directly or through an intermediate roll by a single row of axially short backing rolls, each of which is carried in a carrier pivoted to a rigid member of the mill frame, the pivots of all the carriers associated with each work roll being aligned with one another, said mill including means for applying a substantially constant loading force to each of said carriers, the work rolls also being contacted by reaction rolls which contact the work rolls in such a manner that the reaction is substantially parallel with the plane of the strip pass between the work rolls to absorb the loads which arise in at least one direction parallel to the strip during rolling.

The flexibility of the work rolls should be matched to the purpose for which the mill is to be employed in accordance with the principles already set out in U.S. Pat. No. 3,429,166.

Reaction rolls may be provided on both sides of the work rolls and in such case the axes of the backing rolls lie on the plane'passing through the axes of the upper and lower work rolls. Alternatively reaction rolls may be employed on one side only of the work rolls, the reaction on the other side of the work rolls being provided by the backing rolls which are so arranged that the line of application of pressure to the work rolls is offset from the plane passing through the axes of the work rolls, the amount of said offset for each work roll being such that the plane passing through said line and the bite of the work rolls makes a small angle with the plane passing through the axes of the work rolls, said angle being preferably less than 10.

It is found with the arrangement of the present invention, in which there is only a single row of backing rolls in contact with each work roll, that the accuracy of the alignment of the pivots of the backing roll carriers is no longer as critical as in the earlier apparatus described in U.S. Pat. No. 3,429,166. It can be shown that the tolerable pivot misplacements are more than ten times higher than those tolerable in the earlier apparatus and no difficulty is experienced in satisfying these tolerances by conventional workshop practices.

Referring now to the accompanying drawings:

FIG. 1 illustrates an apparatus made in accordance with the principles of the present invention,

FIGS. 2 and 3 respectively illustrate two different systems for varying the loading applied through the outermost loaded backing roll,

FIG. 4a illustrates an individual hydraulic cell,

FIG. 4b illustrates a modified individual hydraulic cell, and

FIGS. 5a, 5b and 5c illustrate modified forms of apparatus.

FIG. 6 is a fragmentary elevational view across the mill, looking from the left in FIG. 1 and FIG. 7 is view similar to FIG. 6, but showing individual loading cells and a loading control system as in FIG. 3.

Referring now to FIG. 1, there is illustrated diagrammatically a rolling mill, from which the main frame elements have been omitted. In the drawing upper and lower main beams are indicated at 1 and 2 to provide the ultimate support for the thin and flexible work rolls 3 and 4, which may be driven rolls or which may be undriven and be turned by contact with the strip which is pulled through the rolls for the purposes of rectification of bad shape. The loading support for the work rolls 3 and 4 is by means of axially short backing rolls 5, each supported in an individual carrier 6 pivoted to the respective beams 1 and 2 on the pivot axes 7. The longitudinal clearance between the backing rolls 5 is kept as small as possible, consistent with the special requirements of the carriers 6. Typically the axial length of the backing rolls 5 is about 1-2 inches and the space between adjacent backing rolls is of the order of onehalf inch. Hydraulic capsules 8, which may be extended mattress-like elements as shown in FIG. 6 (or individual load cells for each carrier 6 as described below for FIG. 7), are arranged between the carriers 6 and wedges 9, supported by the respective mill beams l and 2 and having an angularity such that their surface is substantially normal to the line of reaction between the work rolls 3 and 4 and their backing rolls 5. In order to overcome the difiiculty previously mentioned which is due to the long capsules and results in misalignment of the work rolls in relation to the mill beams, one of the hydraulic capsules 8 may be divided into two mutually isolated halves, 8a and 8b (FIG. 6).

Reaction rolls 10 are carried in carriers 11 pivoted to the mill structure along the same pivot axis as the carriers 6. The position of the carriers 11 is adjusted by wedges 12 so as to ensure that the reaction between the work rolls and the reaction rolls is substantially parallel with the strip pass plane indicated at 14.

With this arrangement it is found that the variation of load imparted by the individual backing rolls 5 to their associated work rolls is easily kept within 1 or 2 percent despite misalignment of the order of 2 X 10' inches between the pivot axes of the aligned backing roll carrier pivots. This holds true even though the reaction between the work rolls and the reaction rolls may be as high as 20 percent of the reaction between the work rolls and the backing rolls 5.

As already explained means must be provided for counterbalancing in whole or in part the force applied I to the individual carriers 6 by the associated hydraulic capsule 8. The purpose of such counterbalancing is to off-load all the backing rolls 5 lying outwardly of the edges of the strip under treatment and to permit partial ofi-loading of the backing rolls 5 which overlap the edges of the strip so that the loading applied through the flexible work rolls at the edges of the strip may be matched to the strip width. The position of suitable latching members is indicated at 15. Such latching members may take the form of spring-loaded hooks, but are preferably constructed as shown in FIG. 2 or are replaced by a control system as shown in FIG. 3. The arrangements shown in FIGS. 2 and 3 are equally applicable for use in the rolling mill illustrated in FIG. 1 and in the various constructions of rolling mill described in US. Pat. No. 3,429,166.

In the system of FIG. 2 a latching bolt 16 is arranged to engage a backing roll carrier 6 at the position indicated by the line 15 in FIG. 1 to apply a variable lifting force on the carrier 6 so as to counteract or counterbalance in whole or in part the force applied to the carrier 6 by the hydraulic capsule 8. The latching bolt 16, applied at its lower end (not shown, but similar to the latches 15 in the cited Patent) to a carrier 6 which requires counterbalancin'g, is pivotally connected to a lever 17, the movement of which is limited by upper and lower stops 18. Movement of the lever 17 is due to a hydraulic load cell 19 which is connected by tube 20 to the main hydraulic system of the mill so that the hydraulic pressure in the load cell is substantially constant. The lever 17 is provided with a movable fulcrum 21, which is in contact with it at a point between its connection to the latch bolt 16 and its connection to the load cell 19. The movable fulcrum 21 is controlled through a rod 22 which moves it lengthways in a guideway formed on a stationary member 23 of the main mill frame. The member 23 can be part of member 1 or 2, through which the bolt 16 can slide as at 15 in FIG. 1, and the load cell 19 is engaged, as shown, between the lever 21 and another stationary part of the mill frame, e.g. a spaced part of member 1 or 2. It will be readily seen that as the fulcrum 21 is moved to the left from a position directly beneath the center of the hydraulic cell 19 the force applied to the latching bolts to counteract the loading applied by the hydraulic capsule increases. The rod 22, by means of which the longitudinal position of the fulcrum 21 is adjusted, may itself be moved manually, but is preferably moved in response to guides which sense the position of the edges of the strip being rolled. It is possible to provide a self-centering action in response to inward or outward wandering of the strip edge. In the case of outward wandering the loading of the strip edge applied through the relevant backing roll 5 may be increased to such an extent as to cause slight long edge and this would tend to steer the strip back to a central position. Since outward wandering at one edge will be accompanied by inward wandering at the other edge the loading at the other edge is simultaneously decreased to such extent that the second edge is rolled slightly short edge.

A suitable hydraulic loading cell for use in the system of FIG. 2 and of FIG. 3 and also for loading individual carriers as at and 8d of FIG. 7 is illustrated in FIG. 4a and consists of a body 30 having a fluid space 31 provided with a pair of fluid connections 32, which form the only outlet for the space 31 which is otherwise enclosed by the body 30 and a flexible diaphragm 33 held in position on the body 30 by means of a clamp ring 34 held in position by studs 35. The diaphragm 33 preferably carries a member 36 which has an external diameter very close to the internal diameter of the ring 34. The thrust face of the member 36 ill usually be coated with a low friction material so as to permit it to be used to apply thrust directly to a lever.

In an alternative construction illustrated in FIG. 4b-

the diaphragm 33 is replaced by an axially short enclosed rubber capsule 33a which fills the space 31 and is held in position by the inner edge of the ring 34, which overlaps it, a rubber reinforcing gasket 37 being interposed between the ring 34 and the capsule 33a.

In the system illustrated in FIG. 3 and FIG. 7 no mechanical latching rods are employed for resisting the hydraulic pressure applied to the backing roll carriers 6. In this construction the extended mattress-like hydraulic capsules 8 are replaced by individual hydraulic load cells of which there is one for each backing roll carrier as at 80 and 8d in FIG. 7. These individual load cells are constructed as shown in FIG. 4a or FIG. 4b. Those hydraulic load cells 8c which back carriers 6 towards the center of the mill and which will in consequence never require off-loading may be connected directly to a common high pressure line, so as to maintain them at a common pressure. All the remaining hydraulic load cells 8d, which back carriers 6, are connected to individual controlling load cells. Thus a carrier-backing load cell is connected to a load cell 43, with which it forms a closed system; or as-in FIG. 7, to carrier-backing cells 8d requiring identical control may be connected together to a load cell 43, in a like closed system. In the unit of FIG. 3, each load cell 43 is associated with a load cell 40, all of which are interconnected so as to be maintained at a common pressure conveniently the same high pressure as the carrierbacking cells 80. The load cells 40 and 43 are positioned between an abutment surface 44 and a dividing beam 42. Depending upon the position of a movable fulcrum 46 controlled by a positioning rod 47 and bearing against a reaction block 48, the pressure transmitted by the hydraulic load cell 43 to its related carrier-backing load cell can be proportioned in relation to the high pressure transmitted to cell 40 and indeed the slave load cells 43 and their related carrier-backing load cells 8d can in this manner be loaded to any pressure between zero and the pressure of cells 40 or in.- deed to a higher pressure. Since the only functional connection between the device in FIG. 3 and the working parts of the mill is via the hydraulic liquid tubing from the cells 40, 43 (see FIG. 7), the elements 44, 48 can be part of any stationary structure in or near the mill frame. As will be understood, individual carrierbacking load cells are employed for the carriers 6 in the system of FIGS. 3 and 7, and may be employed (for example, instead of the long capsules of FIGS. 1 and 6) in other systems of the invention.

Since the backing rolls 5 are rotatably mounted in the carriers 6, it is inevitable that there be some degree of interval between adjacent backing rolls 5 and where these act directly on the work rolls 3 the areas where the work rolls are in contact with the backing rolls will acquire different surface characteristics from the areas out of contact with the backing rolls unless special measures are taken to prevent this. According to a further feature of the invention the work rolls and the pinion stand through which torque is transmitted to them from the main motor are made so as to be longitudinally movable through a distance of some inches and the movement is produced in small increments of about one-eighth to one-fourth inch by a screw or similar linear drive mechanism which operates automatically each time the roll force is reduced to zero. Preferably the system employs a low area plunger in the hydraulic system to relieve the system pressure immediately prior to the passage of the tail end of the rolling stock through the mill which acts as a normal off-loading safety device for the mill and this may also be utilized to initiate the movement of the sliding piston stand.

FIGS. 5a, 5b and 5c illustrate alternative arrangements of the mill of FIG. 1. Like parts are indicated by like reference numerals. In these arrangements intermediate rolls 50 are interposed between the backing rolls 5 and the work rolls 3 and 4. In FIG. 5a all operative roll axes lie in the same plane. The intermediate rolls 50 and work rolls are retained in position by continuous reaction rolls 51 and 52. The reaction rolls 51 and 52 are supported in continuous semi-circular plain bearings or alternatively by closely adjacent roller bearings. The reaction rolls 51, 52 are thus held rigidly against sagging and against bending in the plane of the strip, those on the entry side of the mill being reactively fixed, but adjustable for roll positioning, whilst those on the exit side are carried in slides and are stabilized by preloading rams 53, 54. In FIGS. 5b and 5c, the backing rolls 5 are offset from the vertical, the intermediate rolls 50 thus providing steady continuous horizontal reactions which are supported by the reaction rolls 52. The total number of beams and reaction rolls so needed is reduced from those in FIG. 5a as indicated, and further, the reaction rolls 51 (FIG. 5a) are no longer required as the roller bearings 55 (FIGS. 5b and 5c) impinge directly onto the intermediate rolls 50. The ends of the intermediate rolls 50 are held captive to prevent movement when the work rolls 3, 4 are removed, the latter being counterbalanced to maintain the roll gap. 7

These arrangements offer alternative methods of avoiding the potential tramlinef strip marking problem and at the same time considerably attenuates variations in the roll force pattern due to shear strain in the gaps between the backing rolls by the flattening strain between the work and intermediate rolls.

- We claim;

1. A rolling mill comprising flexible upper and lower force to each of said carriers, each said row having its short backing rolls on a common axis and being disposed, and being the only such row so disposed, to apply substantial backing pressure to the corresponding work roll along a line which is on the opposite surface of such work roll from the bite of the work rolls, said mill also including reaction roll means consisting of reaction rolls each disposed in contact with a side of a work roll at a line approximately midway between said backing roll pressure line and said work roll bite, said reaction rolls being in contact with the work rolls in such a manner that the reaction is substantially parallel with the plane of the strip pass between the work rolls to absorb the loads which arise in at least one direction parallel to the strip during rolling.

2. A rolling mill as claimed in claim 1 wherein reaction rolls are provided on both sides of each work roll and the axes of the backing rolls lie on the plane passing through the axes of the work rolls.

3. A rolling mill as claimed in claim 1 wherein reaction roll means along a single axis is provided on one side of each work roll, the reaction on the other side of the work rolls being provided by the backing rolls which are so arranged that the line of application of pressure to the work rolls is offset from the plane passing through the axes of the work rolls, the amount of said offset for each work roll being such that the plane passing through said line and the bite of the work rolls makes a small angle with the plane passing through the axes of the work rolls, said angle being preferably less than 10.

4. A rolling mill as claimed in claim 1 wherein means are provided for varying the loading force applied to at least the carriers near the ends of the work rolls.

5. A rolling mill as claimed in claim 4 wherein the means for applying a loading force to the carriers includes individual hydraulic load cells.

6. A rolling mill as claimed in claim 5 wherein the hydraulic load applied by at least some of said load cells is controllably variable.

7. A rolling mill as claimed in claim 6 wherein the hydraulic load cell associated with a carrier is controlled by a unit which includes a slave hydraulic load cell, to which it is connected in a closed system and a master hydraulic load cell connected to all other master load cells, each master load cell and slave load cell bearing against a lever having a movable fulcrum, whereby the pressure in the carrier load cell may be maintained at a desired proportion of the master load cell pressure.

8. A rolling mill as claimed in claim 2 wherein the reaction rolls on the side of the work rolls remote from the strip input are carried in slides and are stabilized by preloading rams.

9. A rolling mill as claimed in claim 1 wherein the means for applying a loading force to the carriers includes individual hydraulic load cells. 7

10. A rolling mill as claimed in claim 3 wherein the means for applying -a loading force to the carriers includes individual hydraulic load cells. 

1. A rolling mill comprising flexible upper and lower work rolls, each work roll being backed either directly or through an intermediate roll by a single row of axially short backing rolls, each of which is carried in a carrier pivoted to a rigid member of the mill frame, the pivots of all the carriers associated with each work roll being aligned with one another, said mill including means for applying a substantially constant loading force to each of said carriers, each said row having its short backing rolls on a common axis and being disposed, and being the only such row so disposed, to apply substantial backing pressure to the corresponding work roll along a line which is on the opposite surface of such work roll from the bite of the work rolls, said mill also including reaction roll means consisting of reaction rolls each disposed in contact with a side of a work roll at a line approximately midway between said backing roll pressure line and said work roll bite, said reaction rolls being in contact with the work rolls in such a manner that the reaction is substantially parallel with the plane of the strip pass between the work rolls to absorb the loads which arise in at least one direction parallel to the strip during rolling.
 2. A rolling mill as claimed in claim 1 wherein reaction rolls are provided on both sides of each work roll and the axes of the backing rolls lie on the plane passing through the axes of the work rolls.
 3. A rolling mill as claimed in claim 1 wherein reaction roll means along a single axis is provided on one side of each work roll, the reaction on the other side of the work rolls being provided by the backing rolls which are so arranged that the line of application of pressure to the work rolls is offset from the plane passing through the axes of the work rolls, the amount of said offset for each work roll being such that the plane passing through said line and the bite of the work rolls makes a small angle with the plane passing through the axes of the work rolls, said angle being preferably less than 10*.
 4. A rolling mill as claimed in claim 1 wherein means are provided for varying the loading forCe applied to at least the carriers near the ends of the work rolls.
 5. A rolling mill as claimed in claim 4 wherein the means for applying a loading force to the carriers includes individual hydraulic load cells.
 6. A rolling mill as claimed in claim 5 wherein the hydraulic load applied by at least some of said load cells is controllably variable.
 7. A rolling mill as claimed in claim 6 wherein the hydraulic load cell associated with a carrier is controlled by a unit which includes a slave hydraulic load cell, to which it is connected in a closed system and a master hydraulic load cell connected to all other master load cells, each master load cell and slave load cell bearing against a lever having a movable fulcrum, whereby the pressure in the carrier load cell may be maintained at a desired proportion of the master load cell pressure.
 8. A rolling mill as claimed in claim 2 wherein the reaction rolls on the side of the work rolls remote from the strip input are carried in slides and are stabilized by preloading rams.
 9. A rolling mill as claimed in claim 1 wherein the means for applying a loading force to the carriers includes individual hydraulic load cells.
 10. A rolling mill as claimed in claim 3 wherein the means for applying a loading force to the carriers includes individual hydraulic load cells. 